Music drives microfluidic device
31 July 2009
Music, rather than electromechanical valves, can drive experimental
samples through a lab-on-a-chip in a new system developed at the
University of Michigan. This development could significantly simplify
the process of conducting experiments in microfluidic devices.
A paper on the research was published online in the Proceedings
of the National Academy of Sciences.
A lab-on-a-chip, or microfluidic device, integrates multiple
laboratory functions onto one chip just millimeters or centimeters in
size. The devices allow researchers to experiment on tiny sample sizes,
and also to simultaneously perform multiple experiments on the same
material. There is hope that they could lead to instant home tests for
illnesses, food contaminants and toxic gases, among other advances.
To do an experiment in a microfluidic device today, researchers often
use dozens of air hoses, valves and electrical connections between the
chip and a computer to move, mix and split pin-prick drops of fluid in
the device's microscopic channels and divots.
"You quickly lose the advantage of a small microfluidic system," said
Mark Burns, professor and chair of the Department of Chemical
Engineering and a professor in the Department of Biomedical Engineering.
"You'd really like to see something the size of an iPhone that you
could sneeze onto and it would tell you if you have the flu. What hasn't
been developed for such a small system is the pneumatics — the
mechanisms for moving chemicals and samples around on the device."
The U-M researchers use sound waves to drive a unique pneumatic
system that does not require electromechanical valves. Instead, musical
notes produce the air pressure to control droplets in the device. The
U-M system requires only one "off-chip" connection.
"This system is a lot like fiberoptics, or cable television. Nobody's
dragging 200 separate wires all over your house to power all those
channels," Burns said. "There's one cable signal that gets decoded."
The system developed by Burns, chemical engineering doctoral student
Sean Langelier, and their collaborators replaces these air hoses, valves
and electrical connections with what are called resonance cavities. The
resonance cavities are tubes of specific lengths that amplify particular
These cavities are connected on one end to channels in the
microfluidic device, and on the other end to a speaker, which is
connected to a computer. The computer generates the notes, or chords.
The resonance cavities amplify those notes and the sound waves push air
through a hole in the resonance cavity to their assigned channel. The
air then nudges the droplets in the microfluidic device along.
"Each resonance cavity on the device is designed to amplify a
specific tone and turn it into a useful pressure," Langelier said. "If I
play one note, one droplet moves. If I play a three-note chord, three
move, and so on. And because the cavities don't communicate with each
other, I can vary the strength of the individual notes within the chords
to move a given drop faster or slower."
Burns describes the set-up as the reverse of a bell choir. Rather
than ringing a bell to create sound waves in the air, which are heard as
music, this system uses music to create sound waves in the device, which
in turn, move the experimental droplets.
"I think this is a very clever system," Burns said. "It's a way to
make the connections between the microfluidic world and the real world
The new system is still external to the chip, but the researchers are
working to make it smaller and incorporate it on a microfluidic device.
That would be a step closer to a smartphone-sized home flu test.
A video demonstration of music moving, splitting and sorting droplets
is available at:
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